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Appendicitis (inflammation of the appendix) is potentially

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Re: Appendicitis (inflammation of the appendix) is potentially fatal [#permalink]

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New post 20 Jun 2016, 06:07
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Surprised to see the comment with most kudos is advocating the wrong answer C.

Argument says:

Before you had a test whereby out of 100 people, say 50 had appendicitis and 50 did not. It correctly identified 50 cases of necessary appendicitis but also mis-diagnosed 20 of them.

Now because the condition is so potentially dangerous, you can live with the extra 20 that got operated un-necessarily.

OA is B because it states

"new procedure gives 98% accuracy so it's better". Going back to our numbers, that's saying we capture the 50 who had appendicitis and now our error is only 2 people. Of those 2 people they don't actually have appendicitis and operating them won't kill them.

So the doctors are happier.
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Re: Appendicitis (inflammation of the appendix) is potentially fatal [#permalink]

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New post 31 Jul 2016, 23:56
GMBA85 wrote:
Which of the following most logically completes the passage?

Appendicitis (inflammation of the appendix) is potentially fatal; consequently, patients with symptoms strongly suggesting appendicitis almost have their appendix removed. The appropriate surgery is low-risk but performed unnecessarily in about 20 percent of all cases. A newly developed internal scan for appendicitis is highly accurate, producing two misdiagnoses for every 98 correct diagnoses. Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since .

A. the patients who are correctly diagnosed with this test as not having appendicitis invariably have medical conditions that are much less serious than appendicitis

B. the misdiagnoses produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it

C. all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis

D. every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms generally associated with appendicitis

E. the only patients who are misdiagnosed using this test are patients who lack one or more of the symptoms that are generally associated with appendicitis

Can someone also explain what does the last line mean?


can someone explain why 'B' is correct.
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Re: Appendicitis (inflammation of the appendix) is potentially [#permalink]

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New post 15 Sep 2016, 09:19
Hi
Can someone explain the difference b/w B and E plz :(
They look almost the same to me..
Been able to eliminate A/C/D
Regards,
Abhishek

nilesh376 wrote:
Appendicitis (inflammation of the appendix) is potentially fatal; consequently, patients with symptoms strongly suggesting appendicitis almost have their appendix removed. The appropriate surgery is low-risk but performed unnecessarily in about 20 percent of all cases. A newly developed internal scan for appendicitis is highly accurate, producing two misdiagnoses for every 98 correct diagnoses. Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since ____________

A. the patients who are correctly diagnosed with this test as not having appendicitis invariably have medical conditions that are much less serious than appendicitis
B. the misdiagnoses produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it
C. all of the patients who are diagnosed with this test as having appendicitis do, in fact,have appendicitis
D. every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms generally associated with appendicitis
E. the only patients who are misdiagnosed using this test are patients who lack one or more of the symptoms that are generally associated with appendicitis
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CR from prep <Appendicitis (inflammation of the appendix) > [#permalink]

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New post 17 Sep 2016, 08:33
Hi,
I know this CR question from prep has been discussed.

"Which of the following most logically completes the passage?

Appendicitis (inflammation of the appendix) is potentially fatal; consequently, patients with symptoms strongly suggesting appendicitis almost always have their appendix removed. The appropriate surgery is low-risk but performed unnecessarily in about 20 percent of all cases. A newly developed internal scan for appendicitis is highly accurate, producing two misdiagnoses for every 98 correct diagnoses. Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since ____________. "

"A. the patients who are correctly diagnosed with this test as not having appendicitis invariably have medical conditions that are much less serious than appendicitis

B. the misdiagnoses produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it

C. all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis

D. every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms
generally associated with appendicitis

E. the only patients who are misdiagnosed using this test are patients who lack one or more of the symptoms that
are generally associated with appendicitis "


However, I am quite confused b/w B and E.
Kindly note that I new to this forum,So pretty unsure about the posting rules.

Reagrds,
Abhishek Sinha
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Appendicitis (inflammation of the appendix) is potentially [#permalink]

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New post 17 Sep 2016, 09:26
2
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abhishek03050 wrote:
Hi,
I know this CR question from prep has been discussed.

"Which of the following most logically completes the passage?

Appendicitis (inflammation of the appendix) is potentially fatal; consequently, patients with symptoms strongly suggesting appendicitis almost always have their appendix removed. The appropriate surgery is low-risk but performed unnecessarily in about 20 percent of all cases. A newly developed internal scan for appendicitis is highly accurate, producing two misdiagnoses for every 98 correct diagnoses. Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since ____________. "

"A. the patients who are correctly diagnosed with this test as not having appendicitis invariably have medical conditions that are much less serious than appendicitis

B. the misdiagnoses produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it

C. all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis

D. every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms
generally associated with appendicitis

E. the only patients who are misdiagnosed using this test are patients who lack one or more of the symptoms that
are generally associated with appendicitis "


However, I am quite confused b/w B and E.
Kindly note that I new to this forum,So pretty unsure about the posting rules.

Reagrds,
Abhishek Sinha


There is no need to open a new topic - just add your comment in the previous thread. For this one, I have merged your new topic with the previous one.

Coming to your query:

Misdiagnosis can be of two types:
False positive: A person who does not have appendicitis is identified as having appendicitis.... this leads to unnecessary operation.
False negative: A person who has appendicitis is identified as not having appendicitis.... this leads to faulty release of the patient without operation.

Option B implies that the misdiagnoses are always "false positive" type. There is no chance of getting a "false negative", i.e. there are 2% false positive misdiagnoses and 0% false negative misdiagnosis.

The latter implies that there is no way that that a person who has appendicitis is identified as not having appendicitis. Hence necessary operations are not going to be reduced, since the test does not produce a single case of "false negative".

On the other hand because the test is 98% accurate (only 2% "false positive" misdiagnosis), there will be drastic reduction of unnecessary operations (though they cannot be eliminated altogether).
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Re: Appendicitis (inflammation of the appendix) is potentially [#permalink]

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New post 17 Sep 2016, 10:03
Hi Sayantan,

Sincere apologies for the inconvenience and the trouble caused.

Went through your explanation. Took me some time to digest it.However, I believe now I have got the
difference. Your Detailing of "False Positive /Negative" helped.

Thanks Again :-D

sayantanc2k wrote:
abhishek03050 wrote:
Hi,
I know this CR question from prep has been discussed.

"Which of the following most logically completes the passage?

Appendicitis (inflammation of the appendix) is potentially fatal; consequently, patients with symptoms strongly suggesting appendicitis almost always have their appendix removed. The appropriate surgery is low-risk but performed unnecessarily in about 20 percent of all cases. A newly developed internal scan for appendicitis is highly accurate, producing two misdiagnoses for every 98 correct diagnoses. Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since ____________. "

"A. the patients who are correctly diagnosed with this test as not having appendicitis invariably have medical conditions that are much less serious than appendicitis

B. the misdiagnoses produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it

C. all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis

D. every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms
generally associated with appendicitis

E. the only patients who are misdiagnosed using this test are patients who lack one or more of the symptoms that
are generally associated with appendicitis "


However, I am quite confused b/w B and E.
Kindly note that I new to this forum,So pretty unsure about the posting rules.

Reagrds,
Abhishek Sinha


There is no need to open a new topic - just add your comment in the previous thread. For this one, I have merged your new topic with the previous one.

Coming to your query:

Misdiagnosis can be of two types:
False positive: A person who does not have appendicitis is identified as having appendicitis.... this leads to unnecessary operation.
False negative: A person who has appendicitis is identified as not having appendicitis.... this leads to faulty release of the patient without operation.

Option B implies that the misdiagnoses are always "false positive" type. There is no chance of getting a "false negative", i.e. there are 2% false positive misdiagnoses and 0% false negative misdiagnosis.

The latter implies that there is no way that that a person who has appendicitis is identified as not having appendicitis. Hence necessary operations are not going to be reduced, since the test does not produce a single case of "false negative".

On the other hand because the test is 98% accurate (only 2% "false positive" misdiagnosis), there will be drastic reduction of unnecessary operations (though they cannot be eliminated altogether).
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Re: Appendicitis (inflammation of the appendix) is potentially [#permalink]

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New post 09 Jul 2017, 10:18
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Please explain this if you were to explain it to a 10 year old :/
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Re: Appendicitis (inflammation of the appendix) is potentially [#permalink]

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New post 31 Jul 2017, 12:52
Merged topics. Please, search before posting questions!
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Appendicitis (inflammation of the appendix) is potentially [#permalink]

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New post 02 Aug 2017, 06:49
sayantanc2k wrote:
abhishek03050 wrote:
Hi,
I know this CR question from prep has been discussed.

"Which of the following most logically completes the passage?

Appendicitis (inflammation of the appendix) is potentially fatal; consequently, patients with symptoms strongly suggesting appendicitis almost always have their appendix removed. The appropriate surgery is low-risk but performed unnecessarily in about 20 percent of all cases. A newly developed internal scan for appendicitis is highly accurate, producing two misdiagnoses for every 98 correct diagnoses. Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since ____________. "

"A. the patients who are correctly diagnosed with this test as not having appendicitis invariably have medical conditions that are much less serious than appendicitis

B. the misdiagnoses produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it

C. all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis

D. every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms
generally associated with appendicitis

E. the only patients who are misdiagnosed using this test are patients who lack one or more of the symptoms that
are generally associated with appendicitis "


However, I am quite confused b/w B and E.
Kindly note that I new to this forum,So pretty unsure about the posting rules.

Reagrds,
Abhishek Sinha


There is no need to open a new topic - just add your comment in the previous thread. For this one, I have merged your new topic with the previous one.

Coming to your query:

Misdiagnosis can be of two types:
False positive: A person who does not have appendicitis is identified as having appendicitis.... this leads to unnecessary operation.
False negative: A person who has appendicitis is identified as not having appendicitis.... this leads to faulty release of the patient without operation.

Option B implies that the misdiagnoses are always "false positive" type. There is no chance of getting a "false negative", i.e. there are 2% false positive misdiagnoses and 0% false negative misdiagnosis.

The latter implies that there is no way that that a person who has appendicitis is identified as not having appendicitis. Hence necessary operations are not going to be reduced, since the test does not produce a single case of "false negative".

On the other hand because the test is 98% accurate (only 2% "false positive" misdiagnosis), there will be drastic reduction of unnecessary operations (though they cannot be eliminated altogether).


For me, this is a very hard question. Sayantan, any tips in general to improve ones analytical bend as much as possible? I dont think that any prep course technique would be able to help much in such questions; it would be come down to one's analytical skills.
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Appendicitis (inflammation of the appendix) is potentially [#permalink]

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New post 15 Nov 2017, 19:49
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This question is a bit ridiculous and hinges on people's knowledge of false-positives and false-negatives, which I don't think is very fair.

Let's explain B in extreme simple terms so that people can understand - probably grammatically odd but I'm going to try to convey the message in extreme simple terms.


Necessary Surgeries: Perform surgery on ALL PEOPLE that actually HAVE ISSUE.
Unnecessary Surgeries: Perform surgery on ANYONE that DO NOT HAVE ISSUE.

False-positive: People who DO NOT HAVE ISSUE shown as HAVE. This increases unnecessary surgeries.
False-negative: People who HAVE ISSUE shown as NOT. This decreases necessary surgeries.


Statement: TEST DECREASES Unnecessary Surgeries (given in previous statements); yet TEST does NOT DECREASE Necessary Surgeries because ________.

From statements above, clearly if there are NO False-Negatives then there will be NO DECREASE in Necessary surgeries.

(B) All misdiagnosis are FALSE-POSITIVES. In other words, there are NO False-Negatives.
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Appendicitis (inflammation of the appendix) is potentially [#permalink]

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New post 03 Jan 2018, 22:42
earlier 100 total cases
80 correct , 20 incorrect

Now total 100 same
98 correct and only 2 incorrect

but 80 correct are part of 98 correct in new
and we know 20 incorrect surgery are actually incorrectly done
so how come 98 become 98 including 80 from previous=> by adding 18 from the 20 incorrect ones ( surgery) to the 80
so in new scan 80 are correct and 18 are incorrect that we know

argument say 98 correct and 2 incorrect
now agree 2 incorrect is true

so if we assume 98 surg are correct => and these 98 surgeries include 80 correct
means machine has incorrectly attributed 18 false cases to someone who does not have appendicitis

Lets see option B

the misdiagnoses (18) produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it

BINGO

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Re: Appendicitis (inflammation of the appendix) is potentially [#permalink]

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New post 07 Apr 2018, 19:56
Hi Experts / sayantanc2k / VeritasPrepKarishma

Though I understand the solution, I am not too sure about choice C.

In my opinion choice C weakens the conclusion. If all the patients with append. do have app., then that would mean there are no patients who don't have append. but are diagnosed with append. But we are also told that 2% misdiagnosis is there. So this would mean that 2% cases would be of the patients who have append. but the tool misdiagnosed them. This would result in fewer surgeries than the necessary ones, and hence would not support the conclusion. Is my reasoning correct? Thanks very much!

SD
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Re: Appendicitis (inflammation of the appendix) is potentially [#permalink]

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New post 08 Apr 2018, 18:32
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sdlife wrote:
Hi Experts / sayantanc2k / VeritasPrepKarishma

Though I understand the solution, I am not too sure about choice C.

In my opinion choice C weakens the conclusion. If all the patients with append. do have app., then that would mean there are no patients who don't have append. but are diagnosed with append. But we are also told that 2% misdiagnosis is there. So this would mean that 2% cases would be of the patients who have append. but the tool misdiagnosed them. This would result in fewer surgeries than the necessary ones, and hence would not support the conclusion. Is my reasoning correct? Thanks very much!

SD

Quote:
C. all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis

Choice (C) tells us that everyone who tests positive actually does have appendicitis. That means that the 2% comes from people who test negative. Most of those people probably do not have appendicitis, but there will be some people who test negative even though they have appendicitis.

Yes, this would result in fewer surgeries, but it would also mean that NECESSARY surgeries would not be performed. Say that five people test negative even though they have appendicitis. Obviously those people need the surgery to avoid potentially fatal consequences. But they won't get the surgery because they tested negative.

So the number of NECESSARY surgeries is likely to decrease... very bad news for the people in that 2% and, more importantly, it goes against the portion in bold:

Quote:
Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before

I hope that helps!
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Re: Appendicitis (inflammation of the appendix) is potentially   [#permalink] 08 Apr 2018, 18:32

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